Traveling welder



A. WAESCHLE ET AL April 23, 1940.

TRAVELING WELDER Filed April 25,- 1938 8 Sheets-Sheet 1 INVENTOR5.

E www n f A ma. Mm w Zn.

BY 6AM/xiv,

April 23, 1940.

A. wAEscHLE ET AL 2,197,957

TRAVELING WELDER Filed April 25, 1938 8 Sheets-Sheet 2 INVENTORJ. n/ro/v h/flfJc/m f. BY Foei/vr HAL/7N.

ATTORNEYS.

April 23, 1940. A. wAEscHLE ET AL 2,197,957

TRAVELING wELnER Filed April 25, 1938 8 Sheets-Sheet 3 /0 INVENTOR5. A/To/v h/fifsc/uf.

Hoef/W E. HAL/7N.

ATTORNEYS.

April 23, 19.40- A. wAEscHLE Er A1. 2,197,957

TRAVELING WELDER Filed April 25, 1938 8 Sheets-Sheet 4 A. WAESCHLE El AL TRAVELING WELDER Filed April 25, 1938 8 Sheets-Sheet 5 ATTORNEYS.

April 23, 1940. A. wAl-:scHLE Err AL 191957 TRAVELING wELnEn Filed April 25, 1938 8 sheets-sheet s ATTORNEY J'.

April 23, 1940; A. WAESCHLE Er 2,197,951

TRAVELING WELDER Filed April 25, 1938 8 Sheets-Sheet 7 REPEAT WELD TIMER ATTORNEY .S

REPEAT WELD TIMER April 23, 1940.

A. WAESCHLE ET AL TRAVELING' wELDEn 4 Filed April 25, 1938 8 Sheets-Sheet 8 INVENToRs. /i/vron/ A//ffsc/u f. of/fr 5, HLA/IN.

ATTORNEYS` yPatented Apr. 23, 1940 UNITED ASTATES PATENT OFFICE TRAVELING WELDER Application April 25, 1938, Serial No. 204,115

20 Claims.

This invention relates to a traveling spot welder which is adapted to weld on the ily."

In the drawings:

Fig. 1 is a front elevation.

Fig. 2 is a side elevation.

Fig. 3 is a plan view.

Fig. 4 is a fragmentary front elevation partly in section.

Fig. 5 is a section on the line 5-5 of Fig. 4.

Fig. 6 is a section on the line 6-6 of Fig. 4.

Fig. 7 is a section on the line 1 1 of Fig. 5.

Fig. 8 is a front elevation of the third rail brushes. l

Fig. 9 is a section on the line 9-9 of Fig. 8.

Fig. 10 is a plan view, partly in section, of the electrical conductor connections between the brushes and the transformers.

Fig. 11 is a wiring diagram.

Fig. 12 is a wiring diagram of only one of the limit switch and relay hook ups.

Fig. 1 is a front elevation which shows the machine ready for use on the roof of a Pullman car. The car roof is designated R. 'Ihe track on which the machine travels will be substantially the same curvature as the roof, as is indicated at the bottom of Fig. 1. 'Ihe electrode units are designated by E in Fig. 1, the third rail or bus bar brush unit by B.

Repeat spot welders are not now broadly new. They may be controlled electrically with an E C l: M timer (referred to below) or they may be controlled pneumatically by the reversing valve arrangement shown in the Biederman application, Serial No. 58,916. We desire it to be understood that in carrying out the broad features of our traveling spot Welder, either an electrical control can be used, or a pneumatic control, or, for that matter, a mechanical control may be used, such as a rotating cam shaft, which is old in the prior art. The point is that after the machine has been started once, the timer is set into operation which controls the on cycle, the oil cycle and the one cycle follows the other until the operation of the machine is stopped as by limit switches.

'I'his machine is designed with what we call lagging electrodes, that is to say the electrodes can temporarily remain stationary with the work and then y back to vertical position after the weld is made notwithstanding the machine is traveling all the time. This machine is arranged to travel and work in both directions by reason of vthe reversible stops controlled by the control designated S (Fig. 1).

Now coming to the detail and referring to Figs.

1 and 4: I designates a lever which operates the reversible two-faced stop S (Fig. 4) which is in the form of a segment carried on shaft 3 which is turned by moving lever I. In the position shown in Fig. 4, the stop is arranged to engage with the spring-pressed under-cushion 4 which reciprocates in a cylinder carried on lower bracket 5 attached to the electrode cylinder 6. The upper cushion 'I is carried on bracket 8 which is attached to an extension 9 of electrode cylinder E. This extension 9 pivots the electrode cylinder on the journal III.

With the machine traveling to the left in Fig. 4, the electrode I I moves from the position shown in the full lines to the position shown at the right in the dotted lines. With the machine moving to the right, the electrode moves from the position shown in the full lines to the position shown in the dotted lines at the left. In each of these movements, as soon as the air behind the electrode piston I 3 is released, the air pressure in the return cylinder I4 operates on piston I5 and snaps the electrodes back to the central full line position shown in Fig. d with the stop in the position shown in Fig. 4 where it is arranged 'to stop the electrode in its return to neutral position from the left hand dotted line position, the air will be on the underside of the piston I5.- As the machine travels to the right in Fig. 4, the electrode lagging behind to the left, the piston I5 is pulled down against the resistance of the air pressure. As soon as the repeat control releases the electrode piston I 3, the air pressure on the underside oi' piston I5 snaps the electrode back to central position. 'Ihe impact with the stop 2 is cushioned by the cushion I. Exactly the same operation takes place when the lever I is shifted to the right hand position and the Acushion I at the top cooperates with the face I2 of the stop. But here the air has been turned into the top of the return cylinder I4. This adjustment of the air from the top to the bottom of the piston I5 is automatically made every time the manual control lever I is reversed to start the carriage in its reverse direction. Referring to Fig. 11, it will be seen that when the limit switch 14 is tripped, it deenergizes the solenoid I6 and the valve I8 which controls the ai." line to the return cylinder I I and also the air line to the brush control is returned to neutral position.y When the reversing switch 54 is thrown to close the contacts b, this turns the current through the solenoid I1 and this reverses the air in the cylinders I4 and I9.

This'conveniently brings up next for discussion the unit B (see Fig. 1) which is the bus bar brush unit. It will be noted from Fig. 1 that the brushes at the top are adapted for left hand travel and the brushes at the bottom are adapted for right hand travel. Hence, when the machine is traveling to the left, the air is turned into the top of the cylinder i9 and this brings the upper brushes down into contact with the bus bar. The movement of the platform 20 carrying the brushes is limited by the stop nuts 2| and 22 so that the brushes are only pressed lightly in contact with the bus bar. The bus bar is designated 23. This bus bar has hard copper alloy wear strips 24 at top and bottom so as to take the friction of the copper brushes better than pure copper. The bus bar (see Fig. 9) is a flange of the upright conductor 25 which is bolted to the stationary electrode. 'I'he stationary electrode is curved to the curvature of the roof and rits under the work, as shown in Fig. 9.

There are two transformers T on the carriage (Fig. 1), one for each pair of electrodes. The brushes are connected with a terminal of each transformer by the laminated conductors 21. An examination of Fig. 2 will show the secondary circuit. One terminal 28 of the transformer T is connected with a copper conductor bar 29 that runs up along the throat of the machine. The laminated jumper 30 (Fig. 1) is connected to this conductor bar and, in turn, is connected to the electrode piston rod at 3| (Fig. 5) below the insulation 32. The secondary current then passes through the work into the stationary electrode 26, thence back to the bus bar 23 through the upper or lower set of brushes and thence through the conductor 34 to the conductor 21. The connection between the brushes and the conductor bars 21 is detailed in Fig. 10. The brushes are carried on a block 35 (see Fig. 3) which is mounted on a slide 34 which slides up and down in a track H0, and is electrically connected to the transformers through the laminated conductor 21 (see Fig. 10)

As long as roll 38 is over the work, air pressure is automatically maintained in the top of cylinder 36 (Fig. 4), pushing down piston 31 which forces pressure roll 38 in contact with the work and holds the work strips together. The course of the air can be seen by consulting the wiring and air diagram (Fig. 11) where it will be seen that the cylinder 36 is connected with the valve 39 which is operated by the solenoid 40.

The carriage is operated by an electric motor M (Fig. 3) which drives reduction gearing 4| through a variable speed pulley device. This gearing has a pair of sprocket gears 42 and 43. These, through the chains 44 (Fig. 1), drive the sprocket Wheels 45 and 46 which, in turn, drive the shafts 41 which have sprocket wheels 48 and 49 on their ends. 'I'hese sprocket wheels travel over the stationary chain 50 so as to cause the machine to travel on the track 5I (Fig. 2) on the flanged wheels 53.

The two electrical repeat weld timers indicated in Fig. 11 provide automatic repeat welding control of the particular machine we are describing. Timers of this type are not new and are available on the market. The timer, used on our machine as built, is a product of the Electric Controller & Mfg. Co. of Cleveland, Ohio. In general, this timer controls the successive ons and oifs of the repeat welding cycle through a solenoid-actuated air valve which cuts air pressure alternately into the welding and return sides of the electrode cylinder, in response to electrical impulses from the timer to the solenoid coil of the air valve. Control of the duration of these electrical impulses is eifected in the timer by means of rheostats which can be adjusted to vary the time necessary to charge and discharge condensers. This is a general statement of the mode of operation of this type of timer. However, there are a number of diierent kinds oi electrical repeat weld timers, one of which is described in the Wright Patent No. 2,105,899, that it seems unnecessary to go into the detail of these electrical repeat weld timers as they are complicated and the particular kind of timer used has nothing to do with our invention. Furthermore, as ilrst above stated, it would be permissible to use some other form of timer and repeat weld control, such as a mechcanical one or a pneuematic one, such as shown and described in the Biederman application, Serial No. 58,916.

The mode of operation of our machine may be described as follows (see Fig. 11):

Say that the carriage is on the right hand end of the track. The lever l is thrown to change the position of the stop S (Fig. 4) and, at the same time, operates the reversing switch 54 (as shown in Fig. '1). 'I'he actuating mechanism for reversing switch 54 is so designed that link 55 is not moved until shaft 3 approaches the end of its rotary motion, in order to permit lever I to be turned freeely, with no resisting air pressure against the stops. 'I'his is accomplished by the lost motion between the pin 300 and the adjustable set screws or stops 304, 305. Link 55 operates reversing switch 54, closing its contact a and disconnecting b (Fig. 12). Thereby, coil I8 of air valve I8 is energized building up air pressure in the upper part of cylinder I9 which brings the upper set of brushes in contact with the bus bar 23 and supplies air to the return cylinders I4. Through the same contact a of reversing switch 54, the reversing motor starter 81 is energized through normally closed limit switch 14 on the other end of track. The contacts of motor starter 61 connect the motor M to the line and release the brake |00. Now the carriage moves toward the left. Trip 65a will close the normally open contact of limit switch '13a momentarily which completes the coil circuit of relay 13, that is, starting from line LB through closed contact of reversing switch 54 through limit switch 14, through normally closed contact of limit switch 11a, through momentarily closed contact of limit switch 13a through coil of relay 13 through fourth nger of reversing motor starter 61 to line Lc. Relay 13 is closed now and is held closed, ai'ter limit switch 13a returns to its normal position, through one of its two contacts which is in parallel with the normally open contact of limit switch 13a. The second contact of relay 13 completes the pilot circuit of the timer I Ma which controls the operation oi welding cylinder 3a.

While the carriage moves continuously to the left, the trip 65a will close limit switch 83a and afterwards 12a. The function oi' those limit switches is similar to the one 13a already described but operating their corresponding relays 69 and 12. Relay 69'closes the circuit of solenoid 40 of air valve 39 which, in turn, allows air pressure to build up in the upper part of cylinder 33 whereby roller 38 is moved downward holding welding stock on the stationary electrode. Relay 12 completes pilot circuit of timer IM which controis the operation of welding cylinder 6.

The function of the repeat weld timer, when set in motion by the closing of the pilot circuit, is

Iii

to furnish electrical energy to the solenoids 59 which will operate the air valves 60 and turn air into the top of the cylinders 6 and 6a and then, when the solenoid is deenergized, reverse the valve which turns air into the lower portion of the cylinders. At the same time, the current is turned into solenoid-controlled primary circuit switches 66 and 16 and these switches are closed, thereby establishing the primary circuit which is, of course, properly timed with respect to the air impulses so that the primary switch is closed after the electrodes engage the work and opened before the electrodes leave the work.

This cycle of operation repeats itself while the carriage moves at practically constant speed. As the carriage approaches toward the left hand side of the track, its trip 65 strikes the limit switch 1Ia. This momentarily breaks the current flowing to the relay 13. The relay hold-in circuit is broken and the relay illes open, breaking the pilot circuit of timer IOIa. Thereafter, trip 65 will strike successively limit switches 69a and 10a whereby the corresponding relay coils 69 and 12 are deenergized. Finally, the trip 65 hits limit switch 1l breaking the motor starter circuit, disconnecting motor M and applying brake and also breaking the current through the solenoid I6 which controls valve I6. The solenoid I6 is deenergized and the air valve I6 returns to neutral position releasing the air in the brush platform actuating cylinder I9 and also in the return cylinders I4.

A new welding operation is started by throwing lever I to the opposite side. This changes the position of the stops and, at the same time, operates reversing switch l. Contact a of reversing switch 5l is then open and contact b closed. Through this contact, coil I1 of air valve I9 is energized, whereby air is supplied to the lower part of cylinder I9, which brings the lower set of contact brushes in contact with the contact bar, and also to the return cylinders Il to the lower part of the cylinder for the right hand electrode and to the upper part of the cylinder for the left hand electrode. The same contact completes the circuit for the coil of the reversing motor starter releasing brake |00 and starting the motor which propels carriage toward the right. Moving to the right, the trip 65 on the carriage momentarily closes the limit switches 10a and 69a and 1Ia successively, energizing their corresponding relays 10, 69 and 1I in a similar way as limit switches 13a, 69a and 12a energized their correspending relays 13, 69 and 12.

Relays 10, 68 and 1I have now the same function as relays 13,l 69 and 12 had when the carriage moved toward the left. The function of the timers and air cylinders are the same as described before and, as the carriage approaches toward the right hand side, limit switch 12a-releases relay 10, limit switch 69a releases relay 69, limit switch 13a releases relay 1I and limit switch 15 deenergizes the reversing motor starter 61, whereby the motor is disconnected and the brake is applied; and also deenergizes solenoid I1 of air valve I6 which returns to neutral position releasing the air in the brush platform actuating cylinder I9 as well as in the return cylinders Il.

It seems here appropriate to describe more in detail how these limit switches are tripped and re-tripped and how the relays operate. Fig. 11 is a complicated wiring diagram so thatin order to explain the operation, we have selected lust one set of relays and two pairs of limit switches. This simplified diagram is Fig. 12. We have taken the limit switches 69a and 69a which control the -relays 68 and 69 which, in turn, control the solenoid 40 that controls the air valve 39 which, in turn controls the pressure roll 39 (Fig. 4). The circuit is traced from line LB, pses through the reversing switch 54, through the motor limit switch 14, through the switch 69a, then to the relay switch 69 but here the circuit is broken. Now, assume that the carriage from its extreme right hand position starts to the left, trip 65a encounters the limit switch 69a and this shorts the current around the broken relay switch 69 and through the solenoid 69h of this switch to the second line Lc. This closes the switch. The left hand switch bar of the relay 69 then closes the circuit from the Lc supply line through solenoid 40 and back to the LB supply line, while current also flows from LB line through the reversing `switch 5I through switch 14, limit switch 69a,

through the right hand bar of relay 69 and around through the solenoid of relay 69, back to the second line Lc. This forms a holding circuit and, consequently, the relay 69 is held closed even after trip 65a releases the right hand limit switch 69a. Solenoid 40, therefore, is energized duringV the entire travel of the carriage to the left and the pressure roll is held against the work. In the same way the other pairs of limit switches and relays (Fig. 11) keep the control circuits of the timers closed. Now the left hand trip 65 approaches the limit switch 69a (Fig. 12). It depresses the switch momentarily. This breaks the current to solenoid of .relay 69 and that switch flies open. This breaks the current through solenoid 40, reversesv valve 39 which reverses the air into the bottom of the cylinder 36 (Fig. 4) and lifts the pressure roll.

The other limit switches operate in the same way on the left hand side, breaking the holding circuits of their corresponding relays. The limit switches are returned to closed position but they do not energize the relays. The reversing switch is now thrown to the right hand position. 'I'his reverses the motor and the trip 65 starts back to the right and again trips limit switch 66a. The current then flows from the LB line through the reversing switch 54,(through limit switch and through the coil of relay 69 through limit switch 68a through normally closed contacts of.

limit switch 69a to line Lc. This throwsthe switch bars closed and this same current now is snorted around limit switch 69a through the left hand bar of relay 69 and through the solenoid of relay 69 to hold the switch closed even after limit switch 69a snaps back to its original or upper position. The current flows from LB line through solenoid l0, the right hand bar of the relay 69 and thence back to the Lc line. All the other limit switches are successively tripped as the carriage moves to the rightand the control circuits of the two timers are closed and kept closed until the carriage trips the limit switches at the right.

What we claim is:

1. A traveling Welder having in combination a traveling carriage for traveling along the work, a stationary electrodeon which the work is supported, an electrode for reciprocating into and out of contact with the work and movable with respect to the carriage to permit the carriage to move while the electrode lags behind in working engagement with the work.

2. A traveling welder having in combination a carriage arranged to move along the work, a stationaryv electrode on which the work is supported and a pivotally mounted electrode which is supported on the carriage so that the electrode may remain stationary in contact with the Work While the carriage moves along the work, means for reciprocating the electrode into and out of contact with the work and means for furnishing current to the electrode at proper times with respect to the reciprocation oi the electrode.

3. A traveling welder having in combination a carriage arranged to move along the work, a stationary electrode on which the Work is supported and a. movably mounted electrode which is supn ported on the carriage so that the electrode may remain stationary in contact with the Worlr` While the carriage moves along the work, means for reciprocating the electrode into and out of contact with the work and means for furnishing current to the electrode at proper times with respect to the reciprocation oi the electrode.

fi. A traveling Welder having in combination a traveling carriage for traveling along the work, a stationary electrode on which the work is supported, an electrode for reciprocating into and out of contact with the Werl; and movable with respect to the carriage to permit the carriage to move while the electrode remains stationary in engagement with the work; and an air cylinder and piston connected to the electrode resisting' the tendency of the electrode to lag behind the carriage when the electrode grips the work and immediately returning the electrode to its initial position after the electrode is released from the work.

5. n traveling Welder having in combination a traveling carriage for traveling along the Work, a stationary electrode on which the worl; is sup" ported, an electrode for reciprocating into and out o1' contact with the work and movable with respect to the carriage to permit the carriage to move while the electrode remains stationary in engagement with the work and means yieldingly resisting the lag of the electrode behind the carriage when the electrode grips the Work and iinmediately returning the electrode to its initial position aiter the electrode is released from gripping relation with the Work.

6. A traveling Welder having in combination a traveling carriage for traveling along the Work, a stationary electrode on which the work is supported, an electrode for reciprocating into and out of contact with the work. and movable with respect to the carriage to permit the carriage to move while the electrode remains stationary in engagement with the workmeans yieldingly resisting the lag of the electrode behind the car riage when the electrode grips the work. and immediately returning the electrode to its initial position after the electrode is released from gripping relation with the Work, means for cushioning the electrode when it is returned to its initial position comprising a pair of yieldable members, one located to be operated when the carriage moves in one direction and the other to operate when the carriage moves in the oppot, site direction, and a reversible stop which can be brought to operate with one cushion or the other depending upon the direction of travel of the carriage.

'7. A traveling Welder having in combination a traveling carriage for traveling along the Work, a stationary electrode on which the Work is supported, an electrode for reciprocating into and out of contact with the Work and movable with respect to the carriage to permit the carriage to move while the electrode remains stationary in engagement with the work, means yieldingy resisting the lagl of the electrode behind the carriage when the electrode grips the Work and immediately returning the electrode to its initial position after the electrode is released from gripping relation with the work, means for cushioning the electrode when it s returned to its initial position comprising a pair of yleldable members, one located to be in operation when the carriage moves in one direction and the other to operate when the carriage moves in the opposite direction, a reversible stop which can be brought to operate with one cushion or the other depending upon the direction of ravel of the carriage and means for reversing said stop comprising a reversing switch, electrical connections and a motor in the circuit formed by said connections for driving the carriage in either direction depending upon the direction in which the current is sent through the electrical connections by the reversing switch.

8. A traveling welder having in combination a carriage arranged to move along with the Work, a stationary electrode on which the work is supported and a pivotally mounted electrode and electrode cylinder having an extension which is supported on the carriage so that the electrode may remain stationary in Contact with the Work while the carriage moves along the Work, means for reciprocating the eectrode into and out of Contact with the work, means for furnishing current to the electrode at proper 'times with respect to the reciprocation of the electrode, a cushion supported on the extension of the electrcde cylinder beyond the pivot, and a second cushion supported on the electrode cyiinder on the opposite side of the pivot and a rotatable stop reversible to bring the stop into operative relation with one or the other of the cushions depending upon the direction of movement of the carriage.

9. In a traveling Welder, the combination of a traveling carriager a stationary electrode on which the Work is laid, an electrode movably mounted on the carriage and arranged to lag i behind the carriage when it grips the work while the carriage is moving, means adjacent the electrode and movable with the carriage for pressing against the work to hold the Work and fluid means for coincidentally forcing the electrodes into contact with the work and also forcing the said pressure means into movable contact with the work.

10. In a traveling Welder, the combination of a stationary electrode on which the work rests,

a bus bar connected electrically with the stationary electrode, a carriage movable along the stationary electrode and the work and having a reciprocable electrode movably mounted on the carriage to lag behind the carriage when it grips the work, a set of brushes mounted on the carriage for wiping the bus bar as the carriage moves along the Work for completing a secondary circuit and electrical connections including a transformer coil between the brushes and the movable electrode.

11. In a traveling Welder, the combination of a stationary electrode on which the work rests, a bus bar connected electrically with the stationary electrode, a carriage movable along the stationary electrode and the work and having a reciprocable electrode, a set of brushes mounted on the carriage for wiping the bus bar as the carriage moves along the work for completing a secondary circuit and electrical connections including a transformer coil between the brushes and the reciprocable electrode, the said brush set being movable into and out of contact with the bus bar.

12. In a traveling welder, the combination of a stationary electrode on which the work rests, a bus bar connected electrically with the stationary electrode, a carriage movable along the stationary electrode and the work and having a reciprocable electrode and two sets of brushes located on opposite sides of the bus bar and arranged to be alternatively brought into wiping engagement with the bus bar to complete the secondary circuit, the direction of movement of the brushes depending upon the proposed direction of travel of the carriage.

13. In a traveling Welder, the combination with a secondary circuit including a stationary electrode on which the work rests and a bus bar connected electrically with the stationary electrode, of a carriage movable along the stationary electrode and the work and having a reciprocable electrode and two sets of brushes located on opposite sides of the bus bar and arranged to be alternatively brought into wiping engagement with the bus bar to complete the secondary circuit, depending upon direction of travel of the carriage and a block for supporting the brushes in sliding and wiping relation with a portion of the remainder of the secondary circuit.

14. In a traveling welder, the combination of a stationary electrode on which the work is supported, a carriage, an electrode movable with respect to the carriage to permit the electrode to lag behind the carriage when the electrode grips the work, pneumatic pressure means for returning the electrode to its neutral position, welding circuits including a set of brushes and a third rail into contact with which the brushes are pressed, pneumatic means for moving the brushes, a. reversible motor for causing the carriage to travel, a limit switch which is automatically tripped by the carriage when it reaches the limit of its movement for reversing the motor and a reversing switch for reversing the motor and reversing the air into both pneumatic means to reverse the movement of the brushes and also reverse the uid operating to return the electrode to neutral position.

15. In a traveling welder, the combination of a stationary electrode on which the work is supported, a carriage, an electrode movable with respect to the carriage to permit the electrode to lag behind the carriage when the electrode grips the work, pneumatic pressure means for returning the electrode to its neutral position, welding circuits including a set of brushes and a third rail into contact with which the brushes are pressed, pneumatic means for moving the brushes, a reversible motor for causing the carriage to travel, a limit switch which is automatically tripped by the carriage when it reaches the limit of its movement for stopping the motor, a reversing switch for reversing the motor and reversing the air into both pneumatic means to reverse the movement of the brushes and also reverse the fluid operating to return the electrode to neutral position, a third iluid operated means for causing the electrodes to be raised and lowered with respect to the work, electrical connections, a valve for controlling the fluid to said third fluid means and a second limit switch which is automatically tripped by the carriage near the limit of its movement thereby stopping the raising and lowering of said electrodes.

16. In a traveling welder, the combination of a movable carriage, a welding electrode carried thereon for welding stationary work while the carriage is moving, means for reciprocating such welding electrode repeatedly, a timing control for controlling such repeated reciprocation and limit switching means operated by the carriage at the end of its movement for controlling the timing control.

17. In a traveling Welder, a movable carriage, a welding instrumentality carried thereon, a control for such instrumentality, limit switching means located at each end of the travel of the carriage, a reversing switch for reversing the movement of the carriage, the said limit switching means and reversing switch including electrical circuits, relays, etc., andbeing paired together so that when the carriage trips the limit switch at one end of its travel, it discontinues operation of the control but after the reversing switch is thrown to reverse the movement of the carriage some of the relays can be tripped on the return movement of the carriage to reestablish the control.

18. In a traveling welder, the combination of a movable carriage, means including a motor for moving it back and forth over a prescribed path, a welding instrumentality carried on the carriage, a control therefor provided with a. control circuit, limit switching means for controlling such circuit including a limit switch located at each end of the travel of the carriage and two relays operated each by a solenoid wired to) alford a self-holding circuit, one relay being paired with each limit switch by suitable circuits, and a reversing switch for reversing the current through the motor and the current to the limit switching mechanism, the said members being so arranged that when the limit switch at one end is tripped, a holding circuit is broken and the relay switch closing the said control circuit is broken but whereupon again on the return travel of the carriage with the -reversing switch swung to reversing position, the other relay is closed with its self-holding circuit to reestablish the said control circuit.

19. The combination claimed in claim 18 together with a limit switch for stopping the motor and the supply.

20. The combination claimed in claim 18 including. a pneumatlcally operated commutator brush and a control therefor controlled by a limit switch and also by the reversing switch.

ANTON WAESCHLE. ROBERT Ey ALLAN. 

